This application relates to an apparatus for applying liquid, such as an adhesive or sealant, to the tops of cans or the like, and more specifically to such a device for use in an assembly line to perform this operation at high production. The apparatus of the present invention is particularly adapted for cylindrical cans having walls made of a relatively soft or easily deformed material, such as for example thin wall aluminum cans.
Apparatus of the general type to which the present invention relates is known in the art as exemplified by Cook U.S. Pat. No. 4,413,587. Other patents believed to be less relevant but of general interest are U.S. Pat. Nos. 1,094,139, 2,124,722, 2,388,911, 2,532,914, and 3,695,223. In accordance with the disclosure of U.S. Pat. No. 4,413,587, the cans are moved along a table or slide plate by means of vertically separated timing screws which grip and guide the cans along their path of travel by rotation of the screws. The cans are pressed against the timing screws by contact belts at the opposite sides of the cans, the belts being driven to rotate the cans as they move along their path. The orientation of the cans is adjustable by adjusting the indexing of the two timing screws. In this way the cans can be tilted in a selected position for the application of adhesive at the tops of the cans as explained in the patent. The apparatus and teachings of the referenced patent have proven quite successful with many types of cans. However, the apparatus has some draw backs for use with cans having thin walls or walls of a material that is easily scored or deformed, such as cans of thin wall aluminum. In such applications, the engagement of the timing screws against the cylindrical side walls of the cans required to move the cans linearly along their path of travel, tends to score or deform the walls. This draw back is eliminated with the improvement of the present invention.
In accordance with this improvement the cans are moved or driven along their line or path of travel, and are held in a selected orientation, by restraining means which also move with the cans along the path. Preferably, the restraining means comprise opposing restraining members at each side of the path which are driven on continuous tracks. The opposing members are in registry such they meet at opposite sides of the cans as they enter the apparatus. The opposing members combine to substantially surround the can walls in sufficiently close proximity to hold the can in a selected orientation as it travels along the path and as adhesive is applied to its upper edge. However, the fit between the restraining means and the cans is not so tight as to score or damage the can walls or prevent their rotation. Drive belts at each side of the path engage the cans and cause them to rotate as an adhesive roller applies adhesive to the top edges of the cans.
Hence, a primary objective of the invention is to provide a continuous adhesive applicator which moves the cans along the path of the assembly line and holds them in a selected orientation for application of adhesive to their upper edges without damaging the relatively thin or soft walls of the cans, and without sacrifice in production output. These and other objectives of the invention are apparent from the drawings and detailed description to follow.